Living in Hawaii makes you aware of the shortcomings of the USPS. I received a Christmas present on April 17 (and yes, it was sent in December). A few weeks ago, we Express Mailed some x-rays to Oahu, a distance of about 80 miles as the sooty shearwater flies. It took 6 days. Now, I've got an important shipment on the way and have been "tracking" it at the USPS Web site.
USPS tracking is terrible. When the Express Mail didn't show up in Oahu, I waited through interminable customer-service calls to try to get a tracer going. What I found is that, even if the tracer began (they wouldn't even begin a trace until, I think, 7 days had passed), they don't have detailed information -- there was no way to know where the missing package went astray, whether in the Kona office, in transit, or in Oahu. To me, that means that no one would ever be accountable. UPS and FedEx tracking marks the packages as they move in and off trucks and warehouses.
Unfortunately, USPS is vastly cheaper than UPS or FedEx to the islands.